Tides from Moon–Sun position, and sea waves

GeographyWater & OceansAges 15–16

Viewed from above the North Pole: the pull of the Moon and Sun heaps ocean water into two tidal bulges; as Earth spins, a coastal point (red dot) meets high water and low water about twice a day (period 12 h 25 min). Drag the Moon around its orbit: when Moon, Sun and Earth line up (new moon, full moon) it is spring tide, when they are at right angles (half moon) it is neap tide; a 3-day water-level graph updates continuously. The panel below models wind-driven sea waves — change wind speed and depth to see how height, wavelength, period and breaking waves near shore change.